• Honam Mathematical Journal
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• v.33 no.3
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• pp.355-366
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• 2011

In this paper we investigate criteria that for an irreducible monic quadratic polynomial f(x) ${\in}$ $\mathbb{Q}$[x], $f{\circ}g$ is reducible over $\mathbb{Q}$ for an irreducible polynomial g(x) ${\in}$ $\mathbb{Q}$[x]. Odoni intrigued the discussion about an explicit form of irreducible polynomials f(x) such that $f{\cric}f$ is reducible. We construct a system of infitely many such polynomials.

• Proceedings of the KIEE Conference
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• 1981.07a
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• pp.146-153
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• 1981

A practical and robust control scheme is suggested for MIMO discrete time processes with real simple poles. This type of control scheme, having the advantages of both the adaptiveness and optimality, may be successfully applicable to structured dynamic controllers for plants whose parameters are slowly time-varying. The identification of the process parameters is under-taken in ARMA form and the optimization of the feedback gain matrix is performed in the state space representation with regard to a standard quadratic criterion.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.31 no.7
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• pp.18-24
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• 1982

We derived an optimal control of the Stochastic Bilinear Systems. For that we, firstly, formulated stochastic bilinear system and estimated its state when the system state is not directly observable. Optimal control problem of this system is reviewed on the line of three optimization techniques. An optimal control is derived using Hamilton-Jacobi-Bellman equation via dynamic programming method. It consists of combination of linear and quadratic form in the state. This negative feedback control, also, makes the system stable as far as value function is chosen to be a Lyapunov function. Several other properties of this control are discussed.

• Communications of the Korean Mathematical Society
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• v.37 no.2
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• pp.385-397
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• 2022

Let (M, [ , ]) be a finite dimensional Malcev algebra over an algebraically closed field 𝔽 of characteristic 0. We first prove that, (M, [ , ]) (with [M, M] ≠ 0) is simple if and only if ind(M) = 1 (i.e., M admits a unique (up to a scalar multiple) invariant scalar product). Further, we characterize the form of skew-symmetric biderivations on simple Malcev algebras. In particular, we prove that the simple seven dimensional non-Lie Malcev algebra has no nontrivial skew-symmetric biderivation.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.5
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• pp.391-399
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• 2012

This paper presents a method of hull form design for the assistant vessel which is used both as a lighting boat and a fish carrying boat for the fleet of newly formated purse seiner vessels. The optimum hull form parameters are searched by the Sequential Quadratic Programing(SQP) method with the power estimation method of Van Oortmerssen. The prismatic curve is redesigned from that of the reference hull by the Lackenby method. Through the modification of the hull form by using a CAD system, the design procedure is completed. The resistance performances of the reference and the modified hull forms are estimated by using a numerical simulation method. Also, the estimation of seakeeping ability and stability for the modified hull forms are carried out. And then, an optimum hull form is proposed for the designed hull form. Ship model tests for the reference and the designed hull forms are carried out at ship model basin. The results of the experiments show that the effective horse power of the designed hull form is about 22% smaller than that of the reference hull form at design speed. The designed hull form proposed in this study will contribute to the development of the hull form for Korean large purse seiner vessels.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.5
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• pp.367-375
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• 2012

In this study, hull form of main vessel of Korean large purse seiner fishing industry is developed for the improvement of resistance performance as well as for the satisfaction to the Standard of Fishing Convention, ILO. Through the modification of reference hull form parameters and local characteristics, the hull form development is carried out. The optimum hull form parameters are searched by Sequential Quadratic Programing(SQP) method with the power estimation method of Holtrop & Mannen. To minimize the wave resistance, bulbous bow parameters are determined by the bulbous bow design method of Alvarino. The plasmatic curve is redesigned from that of the reference hull by using Lackenby method. The resistance performances of the reference and designed hull forms are estimated by using numerical simulation method. Also, the judgment of seakeeping ability and the estimation of intact stability for the designed hull form is carried out. As a result, the optimum hull form is proposed. To verify the improvement of resistance performance, model tests are carried out in towing tank. The results show that the resistance of the designed hull form is about 14% smaller than that of the reference hull from at design speed. A new hull form proposed in this study can contribute to the development of the main vessel hull form of Korean large purse seiner fishing system.

• Bulletin of the Korean Mathematical Society
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• v.52 no.4
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• pp.1047-1057
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• 2015

In [6], it is proved that the lengths of periods occurring in the ${\beta}$-expansion of a rational series r noted by $Per_{\beta}(r)$ depend only on the denominator of the reduced form of r for quadratic Pisot unit series. In this paper, we will show first that every rational r in the unit disk has strictly periodic ${\beta}$-expansion for Pisot or Salem unit basis under some condition. Second, for this basis, if $r=\frac{P}{Q}$ is written in reduced form with |P| < |Q|, we will generalize the curious property "$Per_{\beta}(\frac{P}{Q})=Per_{\beta}(\frac{1}{Q})$".

• Journal of Korean Institute of Industrial Engineers
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• v.24 no.1
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• pp.23-35
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• 1998

This article presents a network flow analysis to form flexible machine cells with minimum intercellular part moves and a neural network model to form part families. The operational sequences and production quantity of the part, and the number of cells and the cell size are taken into considerations for a 0-1 quadratic programming formulation and a network flow based solution procedure is developed. After designing the machine cells, a neural network approach for the integration of part families and the automatic assignment of new parts to the existing cells is proposed. A multi-layer backpropagation network with one hidden layer is used. Experimental results with varying number of neurons in hidden layer to evaluate the role of hidden neurons in the network learning performance are also presented. The comprehensive methodology developed in this article is appropriate for solving large-scale industrial applications without building the knowledge-based expert rule for the cellular manufacturing environment.

• Journal of Ocean Engineering and Technology
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• v.24 no.6
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• pp.1-6
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• 2010

A far field approximate solution of the slowly varying force on a 3 dimensional offshore structure in gravity ocean waves is presented. The first order potential, or at least the far field form of the Kochin function, of each frequency wave is assumed to be known. The momentum flux of the fluid domain is formulated to find the time variant force acting on the floating body in bichromatic waves. The second order difference frequency force is identified and extracted from the time variant force. The final solution is expressed as the circular integration of the product of Kochin functions. The limiting form of the slowly varying force is identical to the mean drift force. It shows that the slowly varying force components caused by the body disturbance potential can be evaluated at the far field.

• Journal of applied mathematics & informatics
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• v.5 no.2
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• pp.507-516
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• 1998

In this study we are concerned with the problem of ap-proximating a locally unique solution of an equation on a Banach space. A semilocal convergence theorem is given for the Super-Halley method in Banach spaces. Earlier results have shown that the order of convergence is four for a certain class of operators [4] [5] [8] These results were not given in affine invariant form and made use of a real quadratic majorizing polynomial. Here we provide our re-sults in affine invariant form showing that the order of convergence is at least four. In cases that it is exactly four the rate of convergence is improved. We achieve these results by using a cubic majorizing polynomial. Some numerical examples are given to show that our error bounds are better than earlier ones.